I put an overdrive in a 1954 and was cruising at 75 at 2000 RPM. It had radial tires and was quite comfortable to cruise on the freeway at that speed. The brakes were stock, but with new lining and freshly turned drums, it stopped fine for first stop, but experienced some brake fade after repeated brake use. My 1954 GMC 100 has had the rear end gears changed to 3.08 and it goes around 65 at 2000 RPM with stock 248 GMC and it's not straining at all, again stock brakes all rebuilt work fine.